HALLUCANA: Fixing LLM Hallucination with A Canary Lookahead

Tianyi Li, Erenay Dayanik, Shubhi Tyagi, Andrea Pierleoni


Abstract
In this paper, we present HALLUCANA, a canary lookahead to detect and correct factual hallucinations of Large Language Models (LLMs) in long-form generation. HALLUCANA detects and intervenes as soon as traces of hallucination emerge, during and even before generation. To support timely detection, we exploit the internal factuality representation in the LLM hidden space, where we investigate various proxies to the LLMs’ factuality self-assessment, and discuss its relation to the models’ context familiarity from their pre-training. On biography generation, our method improves generation quality by up to 2.5x, while consuming over 6 times less compute.
Anthology ID:
2025.findings-naacl.12
Volume:
Findings of the Association for Computational Linguistics: NAACL 2025
Month:
April
Year:
2025
Address:
Albuquerque, New Mexico
Editors:
Luis Chiruzzo, Alan Ritter, Lu Wang
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
213–230
Language:
URL:
https://preview.aclanthology.org/Ingest-2025-COMPUTEL/2025.findings-naacl.12/
DOI:
Bibkey:
Cite (ACL):
Tianyi Li, Erenay Dayanik, Shubhi Tyagi, and Andrea Pierleoni. 2025. HALLUCANA: Fixing LLM Hallucination with A Canary Lookahead. In Findings of the Association for Computational Linguistics: NAACL 2025, pages 213–230, Albuquerque, New Mexico. Association for Computational Linguistics.
Cite (Informal):
HALLUCANA: Fixing LLM Hallucination with A Canary Lookahead (Li et al., Findings 2025)
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https://preview.aclanthology.org/Ingest-2025-COMPUTEL/2025.findings-naacl.12.pdf